One thing I noticed, or think I noticed, is that my explorer process is taking 3 to 5 percent CPU time constantly. I don't think this is normal. Secondly, the executable is called explorer.EXE iso. explorer.exe which strikes me as odd since Microsoft usually uses the lower case version. Is that a correct assumption?
Are there any known issues with explorer.exe? I'll look for some tomorrow, since it's bedtime here in Amsterdam.

After a tip from a collegue - thanks Oliver! - I downloaded SiSoftware's Sandra tool. It obviously gave a very bad impression of my CPU and HDD, but then I noticed something...

There were 108 - yes: onehundredandeigth! - versions of AntiVir running! I have no clue how they all got there; must be a glitch in their update scheme I imagine. I can easily see now how 108 antivirus processes, each jumping onto every file I read and write, might slow my machine down a bit. ;oP After I uninstalled AntiVir my machine seemed normal; will try again tonight just to make sure.

I've tried looking at the Avira site for help, found one instance in the fora with the same multiple instances of AntiVir, but for which Avira could not provide a satisfactory solution.

I'll post if this was the culprit, so anyone after me might benefit from this.

I have found one way to get my laptop actually running again: setting the power profile to Gaming or higher. I had set it on Quiet Office. It now looks like this Asus tool is to blame. Why is it so hard to find the culprit...? (

When I use the Gaming or higher profile, my laptop seems to work okay from the get-go. But the Quiet Office settings has worked fine for me until the described problems started. I cannot for the life of me imagine what happened to set this problem off.

Well, I'll just keep ranting away on this thread as events warrant, just to keep someone with similar problems in the future informed. (Here you go, pal!)